Compact Stars in the QCD
Phase diagram
Monday, October 7, 2024 - Friday, October 11, 2024
YITP

Book of Abstracts

iiContents
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1Current Status of Astronomical Observations of Neutron Stars . . . . . . . . . . . . . . .

1Current Status of Astronomical Observations of Neutron Stars . . . . . . . . . . . . . . .

1

Neutron stars and Constraints for the Equation of State of Dense Matter . . . . . . . . .

1

Astrophysics and Nuclear Physics Informed Interactions in Dense Matter: Inclusion of PSR
J0437-4715 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Recent NICER Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Bayesian inference of hybrid neutron star equation of state from multi-messenger astronomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Framework for phase transitions between the Maxwell and Gibbs constructions . . . . .

2

Lattice results for the speed of sound in dense QCD-like theories . . . . . . . . . . . . .

3A study of neutron star property based on the PDM-NJL crossover model . . . . . . . . .

3

Establishing connection between neutron star properties and nuclear matter parameters
through a comprehensive multivariate analysis . . . . . . . . . . . . . . . . . . . . .

4Reconciling constraints from the multi-messenger constraints with the parity doublet model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Reconciling constraints from the multi-messenger constraints with the parity doublet model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
The Effect of Isovector Scalar Meson on Neutron Star Matter Based on a Parity Doublet
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Two-flavor color superconducting quark stars may not exist . . . . . . . . . . . . . . . .

5

Renormalization Group Consistent treatment of NJL Color Superconductivity (online) .

5

Constraining Coupling Parameters of NJL Color Superconductivity for Compact Stars .

6

Holographic model for neutron star with color superconductivity in the inner core . . .

6Equation of state in neutron stars from a bottom-up holographic QCD . . . . . . . . . .

6

Superfluid Band Calculations for Neutron Star Inner Crust . . . . . . . . . . . . . . . . .

6iii

Features of Quarkyonic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7Which first order phase transitions to quark matter are possible in neutron stars? . . . .

7

Possibility of phase transition on superfluid vortex under Higgs-confinement crossover .

8

Heavy Hadron Spectroscopy and Quark Confinement in the Quark Model . . . . . . . .

8Properties of kaon condensation in hyperon-mixed matter with three-baryon repulsion .

8

Impact of hot and cold dense matter on quasinormal oscillation modes in compact stars .

8

Analytic Inversion of the TOV Equation and EOS Predictions From M,R Data . . . . . .

9Twin stars and the QCD phase diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9In memory of Prof. Akira Ohnishi: Hyperon puzzle of neutron stars examined throughheavy-ion collisions and hypernuclei . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Quark nucleation in compact stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
New modelling for hybrid stars with an elastic quark core . . . . . . . . . . . . . . . . . 11
Constraining Quark Matter in Neutron Stars and the prospects of detecting Quark Stars

11

Properties of H particle-admixed compact star . . . . . . . . . . . . . . . . . . . . . . . . 11
3D Pion crystal from the chiral anomaly . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Baryonic Vortex and Magnetic Field Generation . . . . . . . . . . . . . . . . . . . . . . . 12
IAC meeting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Progress and open questions in core-collapse supernova theory . . . . . . . . . . . . . . 12
Parity violation of the weak interaction and supernovae . . . . . . . . . . . . . . . . . . 13
Constraints on dark matter mass-momentum space in light of GW170817 data . . . . . . 13
Gravitational waves from the quark-hadron phase transition . . . . . . . . . . . . . . . . 13
quasi normal oscillations in newly born compact star considering effects of phase transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
On the ejecta properties of binary quark star or quark star-black hole mergers . . . . . . 14
Nucleosynthesis with Quark nugget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
New alternatives of compact stars and related gravitational-wave signatures . . . . . . . 15
Neutron Star in Covariant f(Q) Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Investigating ultra-high-density equations of state through gravitational waves from binary neutron stars mergers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
g-mode oscillations in neutron stars with hyperons . . . . . . . . . . . . . . . . . . . . . 16
Supernova gravitational waves and protoneutron stars . . . . . . . . . . . . . . . . . . . 16
iv

Long term evolution of binary neutron star merger and nucleosynthesis . . . . . . . . . 16
Damping of density oscillations from bulk viscosity in quark matter . . . . . . . . . . . . 17
Study of correlations of nuclear saturation properties and neutron star f mode oscillations
from a machine learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Probing the QCD phase structure with heavy-ion collisions . . . . . . . . . . . . . . . . 17
The energy budget of fast radio burst: Quake from pulsar-like compact star . . . . . . . 18
The status of the Compressed Baryonic Matter experiment at FAIR . . . . . . . . . . . . 18
The low-density EoS under core-collapse supernova and heavy-ion collisions conditions

18

Polarization of thermal dilepton radiation in high-energy heavy-ion collisions . . . . . . 19
Strangeon matter: from stars to nuggets . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Identifying Viable Inhomogeneous Chiral Phases for Neutron Star Matter . . . . . . . . . 20
Effects of charge neutrality and beta equilibrium on the magnetic dual chiral density wave
phase in dense QCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
TBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Sound velocity peak driven by chiral partners in dense two-color QCD . . . . . . . . . . 21
Phase diagram of QCD matter with magnetic field: domain-wall Skyrmion chain in chiralsoliton lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Impact of first-principles calculations on the QCD phase diagram and equation of state .

21

Emulating neutron stars with dipolar supersolids . . . . . . . . . . . . . . . . . . . . . . 21
Exploring dense QCD through hamiltonian lattice simulations in (1+1) dimensions . . .

22

Opening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Heavy Hadron Spectroscopy and Quark Confinement in the Quark Model . . . . . . . . 22
Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
New alternatives of compact stars and related gravitational-wave signatures (online) . .

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58

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59

Current Status of Astronomical Observations of Neutron Stars

60

Current Status of Astronomical Observations of Neutron Stars
I will introduce recent astronomical observations and hot topics of neutron stars and magnetars.

61

Neutron stars and Constraints for the Equation of State of Dense
MatterCorresponding Author: vdexheim@kent.edu
In this talk I review our current understanding of the interior of neutron stars and modern constraints relevant for dense matter. This includes theoretical first-principle results from lattice andperturbative QCD, as well as chiral effective field theory results. From the experimental side, it
includes heavy-ion collision and low-energy nuclear physics results, as well as observations fromneutron stars and their mergers. I also discuss the relevance of isospin, strangeness, and magnetic
fields on the dense and hot equation of state.

62

Astrophysics and Nuclear Physics Informed Interactions in Dense
Matter: Inclusion of PSR J0437-4715
Corresponding Author: tuhin.malik@uc.pt
We investigate how vector and isovector interactions can be determined within the density regime ofneutron stars (NSs) while fulfilling nuclear and astrophysics constraints. We make use of the Chiral
Mean Field (CMF) model, a SU(3) nonlinear realization of the sigma model within the mean-field
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approximation, for the first time within a Bayesian analysis framework. We show that neutronmatter EFT constraints at low density are only satisfied if the vector-isovector mixed interaction
term is included, e.g., a term. We also show the behaviour of the model with respect to the conformal
limit. We demonstrate that the CMF model is able to predict a value for the parameter related to thetrace anomaly and its derivative takes values below 0.2 above four times saturation density within
a hadronic model that does not include {\blu hyperons or} a phase transition to deconfined matter.
We compare these effects with results from other (non-chiral) Relativistic Mean Field models toassess how different approaches to incorporating the same physical constraints affect predictionsof NS properties and dense matter equations of state. We also include data from the gravitation
wave event GW230529 detected by the LIGO-Virgo-Kagra collaboration and the most recent radius
measurement of PSR J0437-4715 from the NASA NICER mission. Our analysis reveals that this new
NICER measurement leads to an average reduction of approximately km radius in the posterior of
the NS mass-radius relationship.

63

Recent NICER Analyses
Corresponding Author: t.h.j.salmi@uva.nl
X-ray pulses of rapidly rotating neutron stars (NSs) can be used to probe both the properties of heatedsurface regions of a NS and the equation of state (EoS) of high-density matter inside a NS. Constraints
on the EoS are obtained by measuring the mass and radius of the NS based on the relativistic effects
when photons travel from the stellar surface to the observer. During the last few years, NICER
telescope has been used to study several rotation-powered millisecond pulsars using this technique.
I will review our latest analysis for the first published pulsar PSR J0030+0451, the massive pulsar PSR
J0740+6620, and the brightest pulsar PSR J0437−4715. In addition, I will discuss our recent progressin applying the pulse profile modeling method to accretion and thermonuclear-powered millisecond
pulsars.

64

Bayesian inference of hybrid neutron star equation of state frommulti-messenger astronomy
Corresponding Author: alexander.ayriyan@gmail.com

65

Framework for phase transitions between the Maxwell and Gibbs
constructions
Corresponding Author: tianqi.zhao@berkeley.edu
By taking the nucleon-to-quark phase transition within a neutron star as an example, we present a
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thermodynamically consistent method to calculate the equation of state of ambient matter so thattransitions that are intermediate to those of the familiar Maxwell and Gibbs constructions can be
described. This method does not address the poorly known surface tension between the two phases
microscopically (as, for example, in the calculation of the core pasta phases via the Wigner-Seitz
approximation) but instead combines the local and global charge neutrality conditions characteristic of the Maxwell and Gibbs constructions, respectively. Overall charge neutrality is achieved by
dividing the leptons to those that obey local charge neutrality (Maxwell) and those that maintainglobal charge neutrality (Gibbs). The equation of state is obtained by using equilibrium constraints
derived from minimizing the total energy density. The results of this minimization are then used
to calculate neutron star mass-radius curves, tidal deformabilities, equilibrium and adiabatic soundspeeds, and nonradial g-mode oscillation frequencies for several intermediate constructions. The
equation of state at finite temperature and off-β-equilibrium, constructed from this framework, canbe used to study the impact of first-order phase transitions in neutron star mergers and core-collapse
supernovae.

66

Lattice results for the speed of sound in dense QCD-like theories
Corresponding Author: itou@yukawa.kyoto-u.ac.jp
We review recent works on the Monte Carlo simulations of dense two-color QCD (QCD) by focusing
on the phase diagram, the equation of state, and the sound velocity at nonzero quark chemical
potential. A possible upper bound of the sound velocity is known as the conformal bound, namely,cs^2/c^2 < 1/3. The sound velocity is below the bound at least in the case of finite-temperature QCD.
However, our recent works show the breaking of this bound in dense QCD. This phenomenon waspreviously unknown from any lattice calculations. We also discuss recent related works including
lattice studies on QCD at nonzero isospin chemical potential, some effective model analyses, and ananalysis based on recent neutron star observations. These works also suggest the breaking of theconformal bound.

67

A study of neutron star property based on the PDM-NJL crossover
model
Corresponding Author: harada@hken.phys.nagoya-u.ac.jp
I will summarize our works in Refs. [1]-[3] in which we studied neutron star property based on
the PDM-NJL crossover model. In the low-density region, we construct an EoS using a hadronicmodel based on the parity doublet structure with the chiral invariant mass of nucleons. In the highdensity region, an EoS is obtained in an NJL-type quark model. By interpolating two EoSs withassuming the quark-hadron crossover, we construct a unified EoS for dense matter. We then derive
the M-R relation of neutron stars from the unified EoS and compare the result with the observational
constraints to obtain an allowed range for the chiral invariant mass.
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68

Establishing connection between neutron star properties and nuclear matter parameters through a comprehensive multivariate
analysis
Corresponding Author: nareshkumarpatra3@gmail.com
We have attempted to mitigate the challenge of connecting the neutron star (NS) properties with thenuclear matter parameters that describe equations of state (EOSs). The efforts to correlate various
neutron star properties with individual nuclear matter parameters have been inconclusive.
A Principal Component Analysis is employed as a tool to uncover the connection between multiple
nuclear matter parameters and the tidal deformability as well as the radius of neutron stars within
the mass range of . The essential EOSs for neutron star matter at low densities have been derived using both uncorrelated uniform distributions and minimally constrained joint posterior distributionsof nuclear matter parameters. For higher densities (fm), the EOSs have been established through asuitable parameterization of the speed of sound, which consistently maintains causality and gradually approaches the conformal limit. Our analysis reveals that in order to account for over 90\% of thevariability in NS properties, it is crucial to consider two or more principal components, emphasizing
the significance of employing multivariate analysis. To explain the variability in tidal deformability
needs a greater number of principal components compared to those for the radius at a given NS
mass. The contributions from iso-vector nuclear matter parameters to the tidal deformability andradius of NS decrease by 25\% with the increase in mass of NS from 1.2 to 1.8.

69

Reconciling constraints from the multi-messenger constraints withthe parity doublet model
Corresponding Author: bikai.gao@gmail.com
The recent discovery of a central compact object (CCO) within the supernova remnant HESS J1731347, characterized by a mass of approximately and a radius of about
km, has opened up a new window for the study of compact objects. This CCO is particularly intriguing because it is the lightest and smallest compact object ever observed, raising questions andchallenging the existing theories. To account for this light compact star, a mean-field model within
the framework of parity doublet structure is applied to describe the hadron matter. Inside the model,
part of the nucleon mass is associated with the chiral symmetry breaking while the other part is fromthe chiral invariant mass which is insensitive to the temperature/density. The value of affects thenuclear equation of state for uniform nuclear matter at low density and exhibits strong correlations
with the radii of neutron stars. We point out that HESS J1731-347 can be explained as the lightest
neutron star for \,MeV.

Young Researcher Session / 70

Reconciling constraints from the multi-messenger constraints withthe parity doublet model
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Compact Stars in the QCD Phase diagram/ Book of Abstracts

Corresponding Author: bikai.gao@gmail.com
The recent discovery of a central compact object (CCO) within the supernova remnant HESS J1731347, characterized by a mass of approximately 0.77+0.20-0.17 Msun and a radius of about 10.4+0.860.78km, has opened up a new window for the study of compact objects. This CCO is particularly
intriguing because it is the lightest and smallest compact object ever observed, raising questions andchallenging the existing theories. To account for this light compact star, a mean-field model within
the framework of parity doublet structure is applied to describe the hadron matter. Inside the model,
part of the nucleon mass is associated with the chiral symmetry breaking while the other part is fromthe chiral invariant mass which is insensitive to the temperature/density. The value of affects thenuclear equation of state for uniform nuclear matter at low density and exhibits strong correlations
with the radii of neutron stars. We point out that HESS J1731-347 can be explained as the lightest
neutron star for 850 MeV.

71

The Effect of Isovector Scalar Meson on Neutron Star Matter Basedon a Parity Doublet Model
Corresponding Author: yukkekong2-c@my.cityu.edu.hk
We study the effect of the isovector-scalar meson (980) on the properties of nuclear matter and theneutron star (NS) matter by constructing a parity doublet model with including the meson based on
the chiral SU(2)L x SU(2)_R symmetry. We also include the - mixing contribution to adjust the slope
parameter at the saturation. We find that, when the chiral invariant mass of nucleon is smaller thanabout 800 MeV, the existence of (980) enlarges the symmetry energy by strengthening the repulsive
meson coupling. On the other hand, for large where the Yukawa coupling of (980) to nucleon issmall, the symmetry energy is reduced by the effect of omega-rho mixing. We then construct theequation of state (EoS) of a neutron star matter to obtain the mass-radius relation of NS. We findthat, in most choices of , the existence of (980) stiffens the EoS and makes the radius of NS larger.
We then constrain the chiral invariant mass of nucleon from the observational data of NS, and findthat 580 < m_0 < 860 MeV for L0 = 57.7 MeV.

72

Two-flavor color superconducting quark stars may not exist
Corresponding Author: wlyuan7@gmail.com
Large uncertainties in the determinations of the equation of state of dense stellar matter allow the
intriguing possibility that the bulk quark matter in beta equilibrium might be the true ground stateof the matter at zero pressure. And quarks will form Cooper pairs very readily since the dominantinteraction between quarks is attractive in some channels. As a result, quark matter will genericallyexhibit color superconductivity, with the favored pairing pattern at intermediately high densities
being two-flavor pairing. In the light of several possible candidates for such self-bound quark stars,
including the very low-mass central compact object in supernova remnant HESS J1731-347 reported
recently, we carry out one field-theoretic model, the Nambu–Jona-Lasinio model, of investigationon the stability of beta-stable two-flavor color superconducting (2SC) phase of quark matter, nevertheless find no physically-allowed parameter space for the existence of 2SC quark stars.

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Renormalization Group Consistent treatment of NJL Color Superconductivity (online)
Corresponding Author: mohogholami@theorie.ikp.physik.tu-darmstadt.de74

Constraining Coupling Parameters of NJL Color Superconductivity for Compact Stars
Corresponding Author: rather@itp.uni-frankfurt.deWe study the Nambu-Jona-Lasinio (NJL) model and its extension to color superconductivity (CSC)
by incorporating the Renormalization Group (RG)-consistent treatment. This refinement leads tosignificant updates in the understanding of the CSC phases including an improved speed of soundat higher densities.
For modeling the dense quark matter EoS, we determine and constrain the vector and diquark coupling parameters based on the current astrophysical constraints from various measurements. Varying the vector and diquark couplings shift the stellar configuration from self-bound to mimicking
gravitational bound for pure strange stars. Furthermore, we observe both stable 2SC and CFL phases
at low vector couplings which change to unstable CFL phases at high values.
We apply these refined couplings to the EoS for the strange stars and hybrid stars, particularly inthe context of neutron star mergers to determine the signatures of CSC phases.

75

Holographic model for neutron star with color superconductivity
in the inner core
Corresponding Author: ahxdhv@gmail.com
In this model holographic model, we will use the Gauss-Bonnet gravity the baryonic matter correspond to the dilute instanton gas and the color superconductivity (CSC) phase is in deconfinement
region. We will calculate this and find the equation of state of the CSC phase76

Equation of state in neutron stars from a bottom-up holographic
QCD
Corresponding Author: iwanaka@rcnp.osaka-u.ac.jp
We derived an equation of state for neutron stars using a bottom-up holographic QCD model. Our calculations included mass-radius relationships of neutron stars and the sound velocity in high-density
QCD matter.

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77

Superfluid Band Calculations for Neutron Star Inner Crust
Corresponding Author: yoshimura.k.ak@m.titech.ac.jp
In the inner crust of neutron stars, a Coulomb lattice of nuclei exists, immersed in a sea of superfluid
neutron gas. The interplay between these nuclear crystals and the background neutrons may significantly alter nuclear dynamics, a phenomenon known as the “entrainment” effect, which is crucial
for understanding several astronomical phenomena.
In our study, we have developed new self-consistent calculations that fully account for both superfluid effects and band structure effects. We have extracted the “effective mass” of free neutrons
through the real-time method.
In this presentation, we will show the formalism and methodology of our calculations, as well as
further extensions towards comprehensive simulations of the subnuclear properties of neutron star
matter.

78

Features of Quarkyonic Matter
Corresponding Author: mclerran@mac.com
I outline the origin of the hypothesis for Quarkyonic Matter and discuss the generic characteristics
of such matter. A specific IdylliQ model is presented corresponding to an ideal gas of nucleons witha constraint that the quark phase space density does not exceed 1, that is the maximal occupancy
for quark states, This model is dual between quarks and nucleons, and in the Quarkyonic phasenucleons largely sit on a Fermi surface surrounded by a filled Fermi sea of quarks. The possibility that the transition density to Quarkyonic matter might be as low as nuclear matter density is
discussed.

79

Which first order phase transitions to quark matter are possible
in neutron stars?
Corresponding Author: jan-erik.christian@uni-hamburg.de
We examine which first order phase transitions are consistent with today’s astrophysical constraints.
In particular, we explore how a well-constrained mass-radius data point would restrict the admissible parameter space and to this end, we employ the most likely candidates of the recent NICER
limits of PSR J0030+0451. To systematically vary the stiffness of the equation of state, we employ
a parametrizable relativistic mean field equation of state, which is in compliance with results fromchiral effective field theory. We model phase transitions via Maxwell constructions and parametrize
them by means of the transitional pressure and the jump in energy density . This provides us witha generic setup that allows for rather general conclusions to be drawn. We outline some regions in
the - parameter space that may allow for a phase transition identification in the near future. We alsofind that a strongly constrained data point, at either exceptionally large or small radii, would reduce
the parameter space to such an extent that mass and radius become insufficient indicators of a phasetransition.
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80

Possibility of phase transition on superfluid vortex under Higgsconfinement crossover
Corresponding Author: dan.kondo@ipmu.jp
At finite densities of three-flavor QCD, a hadron (confinement) superfluid phase is expected to berealized at low densities, and a color superconducting (Higgs) phase at high densities. It is not wellunderstood whether these two phases are connected with or without a phase transition. In thistalk, we consider the Higgs-confinement transition with superfluidity in a U(1)U(1) lattice model
as a simple model. We found that a phase transition occurs on a superfluid vortex, although thebulk system does not exhibit a phase transition. We confirm this phase transition through analytical
calculations using weak/strong coupling expansion and Monte Carlo simulations. We also discusspossible scenarios for QCD.

81

Heavy Hadron Spectroscopy and Quark Confinement in the Quark
Model
Corresponding Author: makoto.oka@riken.jp
I will discuss how multi-quark system confines quarks and propose a new string-type confinement for heavy-tetra-quark systems. It is tested by the fully-heavy tetra-quark (cc c-bar c-bar) system.

82

Properties of kaon condensation in hyperon-mixed matter withthree-baryon repulsion
Corresponding Author: takumi.muto@it-chiba.ac.jp
Possibility of kaon-condensed phase (KC) in hyperon-mixed matter is considered in high-density
multi-strangeness system, which may be realized in neutron stars.
The interaction model is based on effective chiral Lagrangian for kaon-baryon and kaon-kaon interactions, being combined with the relativistic mean-field theory for two-body baryon-baryon (B-B)
interaction. In addition, universal three-baryon repulsive force (UTBR) and three-nucleon attractive
force (TNA) are phenomenologically introduced, where relevant parameters are fixed to satisfy thesaturation properties of symmetric nuclear matter and causality condition.
It is shown that the equation of state (EOS) with KC in hyperon-mixed matter is stiff enough to beconsistent with recent observations of massive neutron stars.
The quark condensates in the presence of KC are also obtained as a function of baryon density, anda role of KC on chiral restoration in the course of hadron-quark transition is discussed.

83

Impact of hot and cold dense matter on quasinormal oscillation
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modes in compact stars
Corresponding Author: vivek.thapa@bacollege.ac.in
A vast ensemble of equations of state (EoSs), developed within the framework of covariant density
functional theory pertaining to hadronic matter and accommodating density-dependent couplings,
is deployed to scrutinize the polar f- and p-oscillations in both cold and hot compact stars. Theinterplay between oscillation frequencies of cold purely nucleonic neutron stars (NSs), their global
parameters, and the characteristics of nuclear matter (NM) is explored by investigating a spectrumof models, which enforce a series of constraints on the saturation properties of NM, pure neutron
matter, and the lower limit of the maximum NS mass within a Bayesian framework. The influences of finite temperature and the presence of exotic particle degrees of freedom, such as hyperons,
Δ-resonances, antikaon condensates, or the transition from hadron to quark phase, are addressed
through the utilization of a suite of models publicly accessible on compose, assuming idealized profiles of temperature or entropy per baryon and charge fraction. Our analysis reveals that finite
temperature effects lead to a reduction in the oscillation frequencies of nucleonic stars, while an
opposite trend is observed for stars harbouring exotic particle degrees of freedom. Furthermore,when employing the Γ-law to construct finite temperature EoSs, errors in the estimation of oscillation mode frequencies range from 10% to 30%, contingent upon the stellar mass. Throughout thisinvestigation, the Cowling approximation is consistently applied.

84

Analytic Inversion of the TOV Equation and EOS Predictions From
M,R Data
Corresponding Author: james.lattimer@stonybrook.edu
An analytic technique of inverting the TOV equation with accuracies within 1% in both energy density and pressure is presented. In addition, a method using correlations connecting M,R data andenergy density,pressure information is presented, giving a method of inferring the EOS from observations that does not contain the usual prior uncertainties stemming from the use of parameterized
or non-parametric EOS techniques.

85

Twin stars and the QCD phase diagram
Corresponding Author: david.blaschke@gmail.com
It has been suggested [1] that the observation of pulsars with the same mass but significantly different radii (twin stars) would prove that the existence of a critical endpoint in the QCD phase diagram
since this phenomenon requires a strong phase transition in cold neutron star matter [2].
We explore whether such a phase transition in neutron star cores, possibly coupled with a secondary
kick mechanism such as neutrino or electromagnetic rocket effect, may provide a formation pathfor isolated and eccentric millisecond pulsars (MSPs) [3].
We find that in compact binary systems (P_orb = 8 days) the accretion-induced phase transition occurs towards the end of mass transfer, specifically during the spin equilibrium phase. In contrast, inbinary systems with wider orbits (P_orb 22 days), this transition takes place during the subsequentspin-down phase, leading to a delayed collapse. We find that a gravitational mass loss of approximately ∆M ∼ 0.01 M suffices to produce an eccentricity of the order of 0.1 without the need of asecondary kick mechanism. Wider systems are more prone to yielding highly eccentric orbits andbe disrupted, presenting a formation path for isolated MSPs [3].
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Compact Stars in the QCD Phase diagram/ Book of Abstracts

We show that in hot neutron star matter during supernova and merger events, thermal twin stars canbe formed [4], even when in the mass-radius diagram of cold neutron stars the branch of hybrid stars
with color superconducting quark matter cores is connected to that of pure neutron stars (no twins).
Investigating systematically star sequences for increasing entropy per baryon s/n_B = const, we finda correlation between the transition to normal quark matter in hybrid star cores, the change fromenthalpic to entropic character of the transition and the occurrence of thermal twin stars at s/n_B ~ 2.
We speculate about a correlation of the thermal twin phenomenon with the supernova explodabilityof massive blue supergiant stars [4]. The result of these investigations has consequeences for theaccessibility of color superconducting quark matter phases in heavy-ion collisions [5].
[1] D. Blaschke, D. E. Alvarez-Castillo and S. Benic, Mass-radius constraints for compact stars and acritical endpoint, PoS CPOD2013 (2013), 063, arXiv:1310.3803 [nucl-th][2] S. Benic et al., A new quark-hadron hybrid equation of state for astrophysics –I. High-mass twin
compact stars, Astron. Astrophys. 577 (2015) A40[3] S. Chanlaridis et al., Formation of twin stars in low-mass X-ray binaries. Implications on eccentricand isolated millisecond pulsar populations, in preparation (2024)[4] J. Carlomagno et al., Hybrid isentropic twin stars, Universe 10 (2024) 336; arXiv:2406.17193[5] D. Blaschke, F. Sandin, V.V. Skokov and S. Typel, Accessibility of color superconducting quark
matter phases in heavy-ion collisions, Acta Phys. Polon. Supp. 3 (2010) 741

86

In memory of Prof. Akira Ohnishi: Hyperon puzzle of neutronstars examined through heavy-ion collisions and hypernuclei
Corresponding Author: jinno.asanosuke.36w@st.kyoto-u.ac.jp
At the beginning of the talk, I will reflect on my memories with my supervisor, Prof. Akira Ohnishi.
Then, I will present our research on the Lambda potential strongly repulsive at high densities thatis capable of avoiding the hyperon puzzle of neutron stars. The Lambda potential is shown to beconsistent with the Lambda binding energies of hypernuclei and the Lambda directed flows in heavyion collision. I will also present my recent studies analyzing the Σ potential to constrain the Λpotential at high densities.

87

Quark nucleation in compact stars
At the extreme densities reached in the core of neutron stars and related astrophysical phenomena,quark deconfined matter may take place. The formation of this new phase of strongly interacting
matter is likely to occur via a first-order phase transition for the typical temperatures reached in
astrophysical processes. For example, quark deconfinement could occur within the hot remnant ofa neutron star merger or within a newly born proto-neutron star. Also, it could possibly represent
the mechanism leading to the explosion of massive blue supergiants.
Within these scenarios, the first seeds of quark matter would form through a process of nucleation
within the metastable hadronic phase. I will address the role of the thermal fluctuations in the
hadronic composition on the nucleation of two-flavor quark matter and its implication for the phenomenology of compact stars. I will discuss in particular how those fluctuations (up to now disregarded in the literature) could substantially increase the rate of nucleation. Moreover, I will also
consider the possibilityof nucleation of absolutely stable three-flavor quark matter that could give birth to stars entirelycomposed of strange quark matter.
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88

New modelling for hybrid stars with an elastic quark core
Corresponding Author: dongzhiyuan0601@gmail.com
Current anisotropic star models often overlook the effects of shear modulus and phase transitions.
In our study, we propose a new anisotropic model for hybrid stars with an elastic quark mattercore and a fluid nuclear matter envelope with a sharp phase transition in between. We incorporate
the effects of shear deformation characterized by the shear modulus into the structural equationsof anisotropic stars by extending the framework established by Karlovini and Samuelsson (2003).
Using this approach, we calculate the anisotropic parameter, , numerically to analyze the impact on
the mass-radius relation and the internal structure of hybrid stars. Additionally, we develop a new
analytical model for anisotropy, as other phenomenological models cannot describe the internal
structure well. The accuracy of our new model is lower than 10%, indicating that the provided
analytical form of σ0 is valid across a broad parameter space.

89

Constraining Quark Matter in Neutron Stars and the prospects ofdetecting Quark Stars
Corresponding Author: swarnim@iucaa.in
Neutron Stars (NSs) make a unique physical laboratory with extreme physical conditions irreproducible in experiments, capable of producing a hadron-to-quark deconfinement phase transition in
their interior. Owing to the high densities reached by the cold nuclear matter at the core of NSs,
it is speculated that NS cores may be composed of deconfined quark matter (QM). Using state-ofthe-art inputs from multi-disciplinary physics (like the chiral effective field theory, astrophysical observations, and perturbative quantum chromodynamics), we impose new constraints on the widelyaccepted phenomenological MIT Bag for deconfined QM in NSs and comment on the phase of matterin NS cores. We include strong interactions to the first order and allow for a mixed phase to model
the system realistically. It is known that if this deconfined QM is more stable than ordinary nuclear
matter, a hypothesis known as the strange quark matter (SQM) hypothesis, such a phase transition
would further lead to the formation of exotic compact objects known as Strange Stars (SSs). We
demonstrate that the future next-generation gravitational wave (GW) detectors hold the potential
to distinguish SS from NSs using simultaneous f-mode and tidal deformability measurements andcan settle the long-standing problem in physics concerning the true ground state of matter.

90

Properties of H particle-admixed compact star
Corresponding Author: wuhaobird@gmail.com
We explore the potential manifestation of a hexaquark, the H particle, as a constituent within neutronstars.
The H particle, characterized by a quark composition of ,is constructed using the framework of Chromomagnetic Interaction (CMI).
Specifically, we contemplate the flavor-singlet state H with .
Our computations indicate that the three-flavor hexaquark state, the H particle, possesses a lower
mass of in comparison to the ,implying greater stability than the two-flavor .
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The analysis involving the H particle is carried out using
the relativistic mean-field (RMF) model.
We investigate the influence of H particle couplings,
a key factor in determining the system stability,and focus on the potential existence of H particle within neutron stars.
We find that H particle could potentially endure as a stable constituent within neutron stars, andlead to a reduction of the maximum mass.

91

3D Pion crystal from the chiral anomaly
Corresponding Author: geraint.evans47@gmail.com
Including the effects of the chiral anomaly within Chiral Perturbation Theory at finite baryon chemical potential, it has been shown that neutral pions form an inhomogeneous phase dubbed the “Chiral Soliton Lattice” (CSL) above a certain critical magnetic field that could possibly be reached inmagnetars and heavy-ion collisions. Beyond a second critical field, the CSL becomes unstable tofluctuations of charged pions, implying they condense. I will point out the similarity of this second
critical field to the upper critical magnetic field in conventional type-II superconductors, suggestingthat an inhomogeneous superconducting charged pion phase exists beyond this point. Applying
similar methods originally used by Abrikosov, I will present results where we’ve constructed sucha phase, and show the region where it is preferred in the baryon chemical potential-magnetic field
phase diagram at zero temperature. This new phase has a non-zero baryon number density whichis periodic in all three spatial dimensions.

92

Baryonic Vortex and Magnetic Field Generation
Corresponding Author: qiuzebin@keio.jp
We propose a vortex carrying baryon number in low energy dense QCD with finite baryon andisospin chemical potentials. The isospin chemical potential is responsible for the charged pion condensate, among which Abrikosov vortex could arise with quantized magnetic flux. Our discovery isthat when the winding of neutral pion is added, such a vortex carries a baryon number conservedby the homotopy of Skyrmion. Then the energy is reduced by a finite baryon chemical potential
through the gauged Wess-Zumino-Witten term. As a result, we reveal that at high baryon density, abaryonic vortex state features energy lower than the homogeneous pion condensates. Such a vortex
bears a self-generated magnetic field indicating applicable scenarios among Magnetar cores.

93

IAC meeting

94
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Progress and open questions in core-collapse supernova theory
Corresponding Author: hirokinagakura1983v20@gmail.com
I will outline the current status of core-collapse supernova (CCSN) theory, and then introduce some
proposed strategies of how the theory can be tested from multi-messenger observations. After underlining the recent progress, I summarize remaining questions on some microphysical aspects of
CCSN theory, paying a special attention to neutrino quantum kinetics or self-induced neutrino flavor
conversions.

95

Parity violation of the weak interaction and supernovae
Corresponding Author: nyama@rk.phys.keio.ac.jp
Neutrinos play essential roles in the evolution of core-collapse supernovae. However, the conventional neutrino kinetic theory violates the basic tenet of low-energy effective theories in that it does
not respect the symmetry (or parity violation) due to the chirality of neutrinos. In this talk, we discuss the formulation of the chiral radiation transport theory for neutrinos with parity violation andits applications to the physics of supernovae and neutron stars.

96

Constraints on dark matter mass-momentum space in light of
GW170817 data
Corresponding Author: ankitlatiyan25@gmail.com
We investigate the effects of dark matter (DM) on neutron star (NS) properties using the relativistic
mean-field (RMF) theory. By integrating a DM model, we analyze how DM parameters, specifically
DM mass and Fermi momentum, influence nuclear saturation properties, the equation of state (EoS),
and the mass-radius relationship of NSs. Our research also examines the universal relation between
dimensionless tidal deformability and compactness in the presence of DM. The inclusion of DM significantly alters nuclear saturation properties, resulting in higher incompressibility and symmetryenergy values. Higher DM Fermi momenta and masses lead to more compact NS configurations with
reduced radii and lower maximum masses, indicating a complex interplay between DM and nuclear
matter. Deviations from the universal relation are observed, notably for NSs with lower compactness. Using observational data from PSR J0740+6620, GW170817, and NICER measurements of PSR
J0030+0451, we derive stringent constraints on the DM parameter space within NSs. Our findings
highlight the necessity of considering DM effects in NS modeling and suggest potential refinements
to current theoretical frameworks to accurately predict NS properties under various astrophysicalconditions. Future work will focus on further refining these models and exploring additional observational data to tighten constraints on DM properties. Furthermore, we acknowledge the importanceof investigating potential decay processes of DM particles and their implications for stellar evolution.

97
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Gravitational waves from the quark-hadron phase transition
Corresponding Author: cuosakwe@ucalgary.ca
It is believed that de-confined quark matter is more energetically stable than hadronic matter at
extreme densities, such as those occurring in neutron stars. We thus believe that an explosive phasetransition between hadronic and quark matter can occur in neutron star cores. Past studies haveshown that the interface between hadronic and quark matter can develop wrinkles as the phasetransition proceeds outward from the core. These wrinkles could cause gravitational wave emission.
This project aims to model that gravitational wave signal using full general relativity.

98

quasi normal oscillations in newly born compact star considering
effects of phase transition
Corresponding Author: anil.1@iitj.ac.in
The massive stars end their lives by supernova explosions, leaving central compact objects that may
evolve into neutron stars. Initially, after birth, the star remains hot and gradually cools down. We
explore the matter and star properties during this initial stage of the compact stars, considering thepossibility of the appearance of deconfined quark matter in the core of the star. Nonradial oscillationin the newly born compact object is highly possible at the initial stage after the supernova explosion.
Non-radial oscillations are an important source of GWs. There is a high chance for GWs from theseoscillations, especially the nodeless fundamental (f-) mode, to be detected by next-generation GW
detectors. We study the evolution in frequencies of non-radial oscillation after birth, considering
the effects due to the presence of deconfined quark matter and predicting the possible signature fordifferent possibilities of theoretical compact star models.

99

On the ejecta properties of binary quark star or quark star-blackhole mergers
Corresponding Author: zq_miao@sjtu.edu.cn
The Bodmer-Witten conjecture proposes that strange quark matter (SQM) is the true ground stateof strong interaction matter, suggesting that self-bound strange quark stars could be the physicalnature of all compact stars. However, distinguishing between quark stars and neutron stars remains
challenging with current astronomical observations. In this talk, I will explore the properties of theejecta coming from binary quark star or quark star-black hole mergers and compare these properties
to those from binary neutron star mergers.

100

Nucleosynthesis with Quark nugget
Corresponding Author: yudong.luo@pku.edu.cn
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During the binary quark star merger, segment quark nuggets could be ripped out. The emission ofneutrons and protons from quark nugget makes the environment differ from the standard binary
neutron star merger. When temperature drops below 1 MeV, the nucleosynthesis path will be different compare with the well-know r-process nucleosynthesis in binary neutron star merger. here inthis talk, I will present the preliminary results on the nucleosynthesis that include the quark nuggets
evaporation and some distinguishable results from the r-process yields.

101

New alternatives of compact stars and related gravitational-wave
signatures
Corresponding Author: iasczhang@ust.hk
Due to the nonperturbative QCD dynamics in the density regime of neutron stars, new alternativesof strong matter and related stellar
structure are possible. Recently, we proposed that up-down quark stars, inverted hybrid stars, hybrid
strangeon stars can possibly exist, based on the hypothesis that either quark matter or strangeon
matter is the ground state of bulk strong matter. They can meet various astrophysical constraints
on masses-radii and tidal deformabilities, some with distinct gravitational-wave signatures that may
help their discriminations in future observations.

102

Neutron Star in Covariant f(Q) Gravity
Corresponding Author: azzam-alwan@hiroshima-u.ac.jp
In this study, we investigate the structure of neutron stars within the framework of covariant gravity,
an extension of general relativity that incorporates non-metricity. By adopting a static and spherically symmetric metric with perfect fluid matter, we derive the modified Tolman-OppenheimerVolkoff (TOV) equations specific to three models: quadratic, exponential, and logarithmic. We analyze the structure profiles and properties of neutron stars, such as mass, radius, and compactness,by employing realistic equations of state (EoS) for nuclear matter. Our results indicate deviationsin the mass-radius relationship of neutron stars when compared to predictions from general relativity, suggesting that non-metricity affects the interior profile of the star. We also demonstrate how
diagrams are compatible with observational constraints from NICER and LIGO.

103

Investigating ultra-high-density equations of state through gravitational waves from binary neutron stars mergers
Corresponding Author: baiotti@ipc.phys.sci.osaka-u.ac.jp
After an introduction to the status of the field, I present our results on how to discriminate equationsof state with a quark-hadron crossover with respect to EOSs with purely hadronic matter or witha first-order quark-hadron transition through gravitational waves emitted in binary neutron starmergers.
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104

g-mode oscillations in neutron stars with hyperons
Corresponding Author: prashanth.jaikumar@csulb.edu
A common alternative to the standard assumption of nucleonic composition of matter in the interiorof a neutron star is to include strange baryons, particularly hyperons. Any change in composition of
the neutron star core has an effect on -mode oscillations of neutron stars, through the compositional
dependence of the equilibrium and adiabatic sound speeds. Using a variety of relativistic mean fieldmodels of dense matter that satisfy observational constraints on global properties of neutron stars,
we predict a sharp rise in the -mode frequencies upon the onset of strange baryons. Should -modes
be observed in the near future, their frequency could be used to test the presence of hyperonic matterin the core of neutron stars.

105

Supernova gravitational waves and protoneutron stars
Corresponding Author: sotani@yukawa.kyoto-u.ac.jp
Supernova gravitational waves are potentially the next candidates to those from the compact binary
mergers. The gravitational waves generally depend on the supernova models, such as the progenitor
mass and equation of state (EOS) for a higher-density region. So, even if one succeeds in detecting
them in the future, it may be difficult to directly extract physical information from them. Up to now,the supernova gravitational waves have mainly been studied via numerical simulations. From such
simulations, the gravitational wave signals are shown, whose frequencies increase from a few hundred hertz to kilo-hertz. On the other hand, the origin of this signal has been unclear. To understandthe gravitational wave signals appearing in numerical simulations, we are studying them with theapproach of asteroseismology. In particular, using the numerical data of simulations we prepare theprotoneutron star models and determine the specific oscillation modes on each time step. Then, we
successfully identify the gravitational wave signals that come from the fundamental oscillations ofprotoneutron stars. In this talk, we also show the recent progress in supernova gravitational waves
with asteroseismology.

106

Long term evolution of binary neutron star merger and nucleosynthesis
Corresponding Author: sho.fujibayashi@gmail.com
The merger of two neutron stars can form a system composed of a central object (either a neutronstar or black hole) and a centrifugally supported disk. Inside the disk, magnetorotational instability
generates a turbulent state, which then induces an effective viscosity. The viscous angular momentum transport and heating can evolve the system and trigger mass ejection from the disk on atimescale of seconds. The post-merger mass ejection contributes to the total ejecta in addition to
the violent merger phase and to shaping the abundance pattern of heavy nuclei produced via ther-process. In this talk, I will present the results of our numerical simulations of such systems andtheir implications.
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107

Damping of density oscillations from bulk viscosity in quark matter
Corresponding Author: cmjm40@gmail.com
We study the damping of density oscillations in the quark matter phase that might occur in compact
stars. To this end we compute the bulk viscosity and the associated damping time in three-flavor
quark matter, considering both nonleptonic and semileptonic electroweak processes. We use twodifferent equations of state of quark matter, more precisely, the MIT bag model and perturbative QCD,
including the leading order corrections in the strong coupling constant. We analyze the dependenceof our results on the density, temperature and value of strange quark mass in each case. Our results
suggest that bulk viscous damping might be relevant in the post-merger phase after the collision of
two neutron stars if deconfined matter is achieved in the process.
We also reviewed the value of the bulk viscosity in different quark matter phases.

108

Study of correlations of nuclear saturation properties and neutron star f mode oscillations from a machine learning
Corresponding Author: dpqraja02@gmail.com
We investigate the intricate relationships between the non-radialmode oscillation frequencies of neutron stars (NS)s and the corresponding nuclear matter equationof state (EOS) using a machine learning (ML) approach within the ambit of the relativistic mean field(RMF) framework for nuclear matter. With two distinct parameterizations of the Walecka model,
namely, (1) with non-linear self interactions of the scalar field (NL) and, (2) a density dependent
Bayesian model (DDB), we perform a thorough examination of the mode frequency in relation tovarious nuclear saturation properties. The correlations between the mode frequencies and nuclear
saturation properties reveal, through various analytical and ML methods, the complex nature of
NSs and their potential as the cosmic laboratory for studying extreme states of matter. A principal
component analysis (PCA) has been performed using mixed datasets from DDB and NL models todiscriminate the relative importance of the different components of the EOS on the mode frequencies. Additionally, a {\it Random forest feature importance} analysis also elucidates the distinct rolesof these properties in determining the mode frequency across a spectrum of NS masses. Our findings are further supported by symbolic regression searches, yielding high-accuracy relations withstrong Pearson coefficients and minimal errors. These relations suggest new methodologies for probing NS core characteristics, such as energy density, pressure, and speed of sound from observationsof non-radial mode oscillations of NSs.

109

Probing the QCD phase structure with heavy-ion collisions
Corresponding Author: vvovchen@central.uh.edu
I will discuss the recent developments for the analysis of QCD phase structure with heavy-ion collisions with an emphasis on the QCD critical point search with event-by-event fluctuations. I will
discuss the dynamical description of proton number cumulants and put these results in the context
of new STAR data from phase II of Beam Energy Scan.
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110

The energy budget of fast radio burst: Quake from pulsar-likecompact star
Corresponding Author: wywang@ucas.ac.cn
With a growing sample of fast radio bursts (FRBs), we investigate the energy budget of different
power sources within the framework of magnetar starquake triggering mechanism.
During a starquake, the energy can be released in any form through strain, magnetic, rotational, andgravitational energies.
{\bf The strain energy can be converted from other three kinds of energy during starquakes.
The following findings are revealed:
1. The crust can store free magnetic energy of erg by existing toroidal fields, sustaining bursts withfrequent starquakes occurring due to crustal instability.}
2. The strain energy develops as a rigid object spins down, which can be released during a global
starquake accompanied by a glitch. However, it takes a long time to accumulate enough strain energy via spindown.
3. The rotational energy of a magnetar with can match the energy and luminosity budget of FRBs.
4. The budget of the total gravitational energy is high, but the mechanism and efficiency of converting this energy to radiation deserve further exploration.

111

The status of the Compressed Baryonic Matter experiment at FAIR
Corresponding Author: kugler@ujf.cas.cz
The Compressed Baryonic Matter (CBM) experiment is currently under construction at the Facility
for Antiproton and Ion Research (FAIR).
Its goal is to explore the phase structure of strongly interacting (QCD) matter at high net-baryon
densities and moderate temperatures through heavy-ion
and hadron collisions in the energy range of \sqrt{s_{NN}} = 2.9 - 4.9 GeV using the SIS100 beams.
As a fixed-target experiment, CBM is equipped with fast, radiation-hard detector systems and an
advanced trigger-less data acquisition scheme.
CBM will operate at interaction rates of up to 10 MHz by performing online space-time reconstruction and event selection,
enabling the measurement of production rate as well as flow of probes such as multi-strange hadrons
and their antiparticles, multi-strange hypernuclei,
and di-leptons, which have not been extensively studied so far.
This presentation will provide an overview of the CBM physics goals, including the investigation of
the equation-of-state of compressed nuclear matter,the potential phase transition from the hadronic to the partonic phase, and chiral symmetry restoration. Experimental data obtained by CBM will have potential to verify
theoretical description of compressed hadronic matter, which is expected to dominate in interior of
the compact stars.
The presentation will cover CBM’s physics performance in areas such as (multi-)strange particle
production, di-lepton spectroscopy and flow phenomena.
Additionally, the status of preparations for CBM’s construction will be reviewed, including performance
evaluations of CBM components in FAIR Phase-0 experiments and the latest results from a CBM
demonstrator test setup operating with SIS18 beams (mCBM).

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112

The low-density EoS under core-collapse supernova and heavyion collisions conditions
Corresponding Author: hpais@uc.pt
Light (e.g. deuterons, tritons, helions, particles) nuclei exist in nature in core-collapse supernova
matter and neutron star (NS) mergers, where temperatures of the order of 50 to 100 MeV may beattained. These clusters not only form in these astrophysical sites, but also in heavy-ion collisions.
The appearance of these clusters can modify the neutrino transport, and, therefore, consequenceson the dynamical evolution of supernovae and on the cooling of proto-neutron stars are expected.
However, a correct estimation of their abundance implies that an in-medium modification of theirbinding energies is precisely derived.
In this talk, we will address the low-density equation of state with the inclusion of light clusters.
We will consider not only from the theoretical point of view how these light clusters are calculated
for warm nuclear matter in the framework of relativistic mean-field (RMF) models with in-medium
effects, but also how these models were calibrated to experimental data from heavy-ion collisions,
measured by the INDRA Collaboration.
We will also analyze the effect of including an exotic state state, such as the tetraneutron, that wasreported in Duer et al, Nature 606, 678 (2022) as a resonant state, on the yields of the other lightclusters. We consider in-medium effects in a two-fold way –that is, via the couplings of the clusters
to the mesons, that were calibrated to the experimental data, and via a binding energy shift –tocompute the low-density equation of state (EoS) for nuclear matter at finite temperature and fixed
proton fraction. We calculate the abundances of the light clusters and chemical equilibrium constants
with and without the tetraneutron. We also analyze how the associated energy of the tetraneutron
would influence such results.
We find that the low-temperature, neutron-rich systems are the ones most affected by the presenceof the tetraneutron, making NSs excellent environments for their formation. Moreover, its presence
in strongly asymmetric matter may increase the proton and particle fractions considerably. This may
have an influence on the dissolution of the accretion disk of the merger of two NSs.

113

Polarization of thermal dilepton radiation in high-energy heavyion collisions
Corresponding Author: wambach@physik.tu-darmstadt.de
Dileptons are one of the most precise probes of the QCD phase diagram in high-energy heavy-ion
experiments. Traversing the fireball undisturbed they yield information about the entire space-time
history of the collision. Over the last decade, a rather consistent picture has emerged in interpretingthe observed inclusive dilepton spectra over a wide range of collision energies. Polarization observables can further elucidate the microscopic emission processes, as they provide independent testsof the longitudinal and transverse components of the virtual photon’s selfenergy. In this talk, I will
present theoretical predictions of these observables based on a realistic model for the in-medium
electromagnetic spectral function. Comparisons to available data from the HADES and NA60 experiments are discussed. They set stage for quantitative polarization studies at FAIR and collider
energies in the future.

114
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Strangeon matter: from stars to nuggets
Corresponding Author: r.x.xu@pku.edu.cn
We draw an analogy between the materials condensed by the strong interaction (i.e., strong matter)and that by the electromagnetic force (simply, electric matter), both of which are condensed matterswith almost continues mass spectrum, if Nature favors the quark-flavor symmetry. While strangeonstars could be manifested in the form of pulsar, gamma-ray bursts and fast radio bursts, strangeon
nuggets would be a dark matter candidate in the standard model of particle physics. Observational
evidence for strangeon matter is discussed.

115

Identifying Viable Inhomogeneous Chiral Phases for Neutron Star
MatterCorresponding Author: incera@gmail.com
Spatial inhomogeneous phases of nuclear and quark matter are a feature of the QCD Phase Map atintermediate densities/low temperatures, making them potential candidates for the inner phases ofneutron stars. Yet, single-modulated chiral condensates, even when energetically favored over others at zero temperature, are wiped out by thermal fluctuations due to the Landau-Peierls instability.
In this work, we discuss a general approach based on simple symmetry arguments to identify a setof single-modulated inhomogeneous chiral phases that can be robust against thermal fluctuations attemperatures compatible with those of neutron stars.

116

Effects of charge neutrality and beta equilibrium on the magnetic
dual chiral density wave phase in dense QCD
Corresponding Author: wgyory@gradcenter.cuny.edu
Recent work has suggested that the magnetic dual chiral density wave (MDCDW), an inhomogeneous condensate that arises in dense QCD in a magnetic field, is an appealing candidate phasefor the description of matter in the core of compact stars. For example, the nontrivial topology inits fermion spectrum gives it a high critical temperature and allows it to avoid the Landau-Peierls
instability, which destabilizes most other inhomogeneous phases at finite temperatures. However,previous studies have not yet examined this phase under the conditions of charge neutrality andbeta equilibrium, which more realistically reflect the environment within compact stars. We areinvestigating charge neutral, beta equilibrated MDCDW, determining how these conditions affectthe order parameters and critical temperature. We also examine the effects of neutrality and beta
equilibrium on the small but nonzero remnant mass that persists at large densities in a magnetic
field, which may lead to interesting chiral transport behavior.

117

TBA
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118

Sound velocity peak driven by chiral partners in dense two-color
QCD
Corresponding Author: daiki.suenaga@kmi.nagoya-u.ac.jp
Recently the lattice simulation in two-color QCD at finite density clarified that the squared soundvelocity cs2 exceeds the conformal limit 1/3 . We know that at mu -> infinity the conformal limit
is realized, thus, a peak structure was numerically observed. Theoretically, on the other hand, the
ChPT is known to predict a monotonic increment of cs2 to yield cs2 -> 1 at sufficiently dense regime,
and fails in deriving the peak. In this talk, I will show that, based on our linear sigma model in dense
two-color QCD, chiral-partner contributions from sigma meson can successfully lead to the peakstructure.

119

Phase diagram of QCD matter with magnetic field: domain-wallSkyrmion chain in chiral soliton latticeCorresponding Author: nishiken@hiroshima-u.ac.jp

120

Impact of first-principles calculations on the QCD phase diagramand equation of state
Corresponding Author: yfuji@uw.edu
We compare two first-principles calculations of the QCD equation of state (EOS): the weak-coupling
results and the recent lattice QCD data at finite isospin density.
Because both finite-baryon-density QCD and finite-isospin-density QCD have the same weak-coupling
expansion, we can learn about the former case from the latter, in which the lattice data is available,
and in this talk, we particularly discuss the effects on (1) the QCD phase diagram and (2) the EOS ofneutron star matter.
Firstly, the weak-coupling results give a small (∼ a few MeV) value for the color-superconducting
gap at quark chemical potential of a GeV order and this implies that the color-flavor locked phase
may not be the ground state even in the perturbative regime of QCD.
Secondly, we discuss the weak-coupling results as the input to the EOS inference for neutron stars.
In such weak-copuling input, there is an undetermined constant (the renormalization scale), which
gives rise to a large uncertainty. We introduce a new prescription to reduce the ambiguity inthe choice of the renormalization scale and discuss its relevance to neutron-star phenomenology.

121

Emulating neutron stars with dipolar supersolids
Corresponding Author: massimo.mannarelli@lngs.infn.it
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In physics, analogies are extremely powerful tools. They give the opportunity to look at physicalphenomena from different perspectives, favoring connections between very disparate research fields.
In a recent work, we established an intriguing analogy between the inner crust of neutron stars andultracold dipolar supersolids and used it to investigate the anomalies in the rotation frequency ofneutron stars, known as glitches.

122

Exploring dense QCD through hamiltonian lattice simulations in(1+1) dimensions
Corresponding Author: yoshimasa.hidaka@yukawa.kyoto-u.ac.jp
We study one-flavor SU(2) and SU(3) lattice QCD in (1+1) dimensions at zero temperature and finite
density using matrix product states and the density matrix renormalization group. We computephysical observables such as the equation of state, chiral condensate, and quark distribution function
as functions of the baryon number density. As a physical implication, we discuss the inhomogeneous
phase at nonzero baryon density, where the chiral condensate is inhomogeneous, and baryons forma crystal. We also discuss how the dynamical degrees of freedom change from hadrons to quarks
through the formation of quark Fermi seas.

123

Opening124

Heavy Hadron Spectroscopy and Quark Confinement in the Quark
Model
Corresponding Author: makoto.oka@riken.jp
I will discuss how multi-quark system confines quarks and propose a new string-type confinement for heavy-tetra-quark systems. It is tested by the fully-heavy tetra-quark (cc c-bar c-bar) system.

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Registration

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Page 22Compact Stars in the QCD Phase diagram/ Book of Abstracts

New alternatives of compact stars and related gravitational-wave
signatures (online)
Corresponding Author: iasczhang@ust.hk
Due to the nonperturbative QCD dynamics in the density regime of neutron stars, new alternativesof strong matter and related stellar structure are possible. Recently, we proposed that up-downquark stars, inverted hybrid stars, hybrid strangeon stars can possibly exist, based on the hypothesisthat either quark matter or strangeon matter is the ground state of bulk strong matter. They canmeet various astrophysical constraints on masses-radii and tidal deformabilities, some with distinct
gravitational-wave signatures that may help their discriminations in future observations.

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